Make sure you have the "game-ready" drivers and not the other one. Nvidia is weird about drivers.
Other than that, try downgrading the drivers. Minecraft uses such an old version of OpenGL that I wouldn't be surprised if new drivers made it slower.
I ran into this problem too, make sure you're using the latest Java 8 JDK and MAKE SURE JAVA_HOME IS SET PROPERLY. Gradle uses the JDK from JAVA_HOME, not the one on your PATH. Specifically, this happens because Java only got support for Let's Encrypt certificates around jdk8_u100 and Forge uses Let's Encrypt.